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Brain Tumor

A brain tumor is any mass created by an abnormal and uncontrolled growth of cells either found in the brain (neurons, glial cells, epithelial cells, myelin producing cells, etc.) or spread from elsewhere (metastasis). Brain tumors are usually located in the posterior third of the brain in childhood and in the anterior two-thirds of the brain in adulthood.

In the United States in 2000, it was estimated that there were 16 500 new cases of brain tumors, which accounted for 1.4% of all cancers, 2.4% of all cancer deaths, and 20%-25% of pediatric cancers. Ultimately, it is estimated that there are 13 000 deaths/year as a result of brain tumors.

brain tumor symptoms and differentiation

Tumors in the brain are either benign or malignant and each has different brain tumor symptoms.

Benign brain tumors include:

  • pituitary adenoma - The diagnosis is generally entertained either on the basis of visual difficulties arising from the compression of the optic nerve by the tumor, or on the basis of manifestations of excess hormone secretion: the specifics depend on the type of hormone. Tumors which cause visual difficulty are likety to be macroadenomas greater than 10 mm in diameter; tumors less than 10 mm are microadenomas.
  • meningioma - The symptoms depend closely on the exact location of the tumor. Hence, a meningioma compressing the frontal lobe can give rise to frontal lobe syndrome.
  • acoustic neuroma - Associated symptoms are unilateral sensorineural hearing loss/deafness and vertigo, while larger tumors can compress local structures, such as the facial nerve, and lead to local symptoms, such as hydrocephalus.

Malignant brain tumors include:

  • glioma (60% of new cases) - Brain tumor symptoms of gliomas depend on which part of the central nervous system is affected. A brain glioma can cause headaches, nausea and vomiting, and cranial nerve disorders as a result of increased intracranial pressure. A glioma of the optic nerve can cause visual loss. Spinal cord gliomas can cause pain, weakness or numbness in the extremities. Gliomas do not metastasize by the bloodstream, but they can spread via the cerebrospinal fluid and cause "drop metastases" to the spinal cord.
  • glioblastoma multiforme (WHO Grade IV glioma) - Common brain cancer symptoms of the disease include seizure, headache, hemiparesis, and personality change.

Some lesions can mimic tumors of the central nervous system. These include tuberculosis of the brain and cerebral abscess.

primary brain tumors

Primary brain tumors are those tumors that originate in the brain, and are named for the cell types from which they originated. Frequently encountered histologic brain tumor types are glioma, glioblastoma, astrocytoma, oligodendroglioma, medulloblastoma, meningioma and neuroglioma. Tumors can be benign and are usually, but not necessarily, localized to a small area. They can also be malignant and invasive (i.e., spreading to neighbouring areas). Brain cells can be damaged by tumor cells by (i) directly being compressed from growth of the tumor; (ii) indirectly being affected from inflammation ongoing in and around the tumor mass, (iii) brain edema (swelling); or (iv) increased pressure in the skull (due to brain edema or to the blockage of the circulation of the cerebrospinal fluid).

Local tissue damage (either by direct or indirect mechanisms) causes focal neurologic symptoms, which vary due to the location of the brain tumor. Hemiparesis, aphasia, difficulty speaking, ataxia, hemihypoesthesia (numbness and decreased sensation of touch on one side of the body) and localized headache are some of the symptoms occurring due to the local effects of the brain tumor. Increased pressure in the skull or brain edema cause more generalized symptoms like generalized headache, nausea and vomiting, loss of consciousness (stupor or coma) and intellectual decline. Seizures due to the local irritating effect of the brain tumor or metabolic changes caused by the cancer are also frequently observed. Since the development of the skull is incomplete during infancy, infants with brain tumor may have increased head perimeter, bulging fontanelles or separated sutures.

Neurologic examination reveals local (specific to the location of the tumor) or generalized neurologic changes. Slowly progressive nature of the neurologic symptoms is suggestive of a possible brain tumor and the diagnosis is confirmed by CT scan or magnetic resonance imaging (MRI) of the head. Angiography, electroencephalography (EEG) or brain biopsy may aid in diagnosis in difficult cases. Although slow progression is an important hallmark of the disease, some brain tumors may enlarge very quickly and thus may cause sudden neurologic changes. Treatment includes the surgical removal of the tumor mass or the destruction of the tumor cells by radiation (radiotherapy) and/or drugs (chemotherapy) in cases with contraindications for a surgical operation.

secondarie brain cancer

Secondary or metastatic brain tumors take their origins from tumor cells which spread to the brain from another location in the body. They are more frequent than primary brain tumors, and are mainly a problem in adults, though children may also have secondary tumors. Approximately one quarter of metastatic cancers spread to brain. Lung cancer and breast cancer are the most common causes of secondary brain tumors. Tumor cells may travel to the brain by blood vessels. Since the brain has no lymphatic drainage system like other organs (cerebrospinal fluid system acts like lymphatic system in the brain), spreading of tumor cells by the lymphatic route (which is very typical for cancers of other organs) is impossible in the brain. In contrast to primary brain tumors, metastatic tumor masses may occur in various remote locations in the brain. Highly aggressive brain tumors like glioblastomas may also be observed in more than one location, but usually in the advanced stages of the disease. Symptoms, diagnosis and treatment are quite similar to those of primary tumors, however in the case of secondary tumors the initial location of the tumor cells must be identified and treated as well.

Primary or secondary, brain tumors may cause herniation of the brain (displacement of one part of the brain tissue due to mass effect of a lesion, usually causing the compression of the neurons controlling the respiratory system in the brainstem and eventually death) and permanent neurologic changes including intellectual decline.

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